Integrating physical and chemical characteristics of lakes into the glacially influenced landscape of the northern cascade mountains, Washington State, USA

A basic knowledge of the physical and chemical characteristics of lakes is needed by management to make informed decisions to protect water resources. In this study we investigated some of the physical and chemical characteri stics of 58 lakes in alpine, subalpine, and forest vegetation zones in a na tural area (North Cascades National Park Service Complex) between 1989 and 1993. The objectives of the study were to: (1) document the time of ice-out relative to lake elevation; (2) determine how a sharp climate gradient wes t and east of the hydrologic divide affected the time of ice-out for subalp ine lakes; and (3) assess how lake water quality was associated with lake e levation, lake depth, and basin geology. As expected, lake ice-out times oc curred earlier with decreasing elevation. East-slope subalpine lakes iced-o ut earlier than did west-slope subalpine lakes because the east slope of th e study area was drier and warmer than the west slope. On average, the lake s were relatively cold, neutral in pH, and low in dissolved substances and concentrations of nitrogen and phosphorus. Although some shallow lakes (dep th <10 m) exhibited the highest alkalinities, conductivities, and concentra tions of phosphorus and nitrogen, most shallow lakes exhibited low values f or these variables that were comparable to values observed in deep lakes. G eology did not play a major role in segregating the lakes based on water qu ality. Overall, lake temperature, pH, alkalinity, conductivity, and concent rations of total phosphorus and total Kjeldahl N increased with decreasing elevation. These changes in water quality with decreasing elevation in this temperate mountainous region corresponded with warmer air temperatures and increased vegetation biomass, soil depth and maturity,and dissolved substa nces and nutrients.